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Appendix I - Continued - 14184_191
Appendix I - Continued - 14184_193

Neets Module 12-Modulation Principles
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AI-4 MASTER OSCILLATOR POWER AMPLIFIER (MOPA)—A transmitter in which the oscillator is isolated from the antenna by a power amplifier. MICROPHONE—An energy converter that changes sound energy into electrical energy. MODULATED WAVE—A complex wave consisting of a carrier and a modulating wave that is transmitted through space. MODULATING WAVE—An information wave representing intelligence. MODULATION FACTOR (M)—An indication of relative magnitudes of the rf carrier and the audio-modulating signal. MODULATION INDEX—The ratio of frequency deviation to the frequency of the modulating signal. MODULATION—The ability to impress intelligence upon a transmission medium, such as radio waves. MODULATOR—The last audio stage in which intelligence is applied to the rf stage to modulate the carrier. MULTIPLICATION FACTOR—The number of times an input frequency is multiplied. MULTIVIBRATOR MODULATOR—An astable multivibrator used to provide frequency modulation by inserting the modulating af voltage in series with the base-return of the multivibrator transistors. NEGATIVE ALTERNATION—That part of a sine wave that is below the reference level. NONLINEAR DEVICE—A device in which the output does not rise and fall directly with the input. NONLINEAR IMPEDANCE—An impedance in which the resulting current through the device is not proportional to the applied voltage. OVERMODULATION—A condition that exists when the peaks of the modulating signal are limited. PEAK AMPLITUDE—The maximum value above or below the reference line. PEAK DETECTION—Detection that uses the amplitude of pam or the duration of pdm to charge a holding capacitor and restore the original waveform. PEAK POWER—The maximum value of the transmitted pulse. PERCENT OF MODULATION—The degree of modulation defined in terms of the maximum permissible amount of modulation. PERIOD—The duration of a waveform. PHASE MODULATION (pm)—Angle modulation in which the phase of the carrier is controlled by the modulating waveform. The amplitude of the modulating wave determines the amount of phase shift and the frequency of the modulation determines how often the phase shifts.






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